1. Field of the Invention
The present invention relates to compositions and methods for treating oil and gas wells to stimulate the production of hydrocarbons therefrom.
2. Description of the Prior Art
The use of acids and other fluids to clean up and stimulate the production of hydrocarbons from subterranean formations penetrated by well bores is well known. The acids and other fluids typically function to improve the natural drainage pattern of the formations and/or to remove barriers within the formations which prevent easy passage of the reservoir fluids through the formations into the well bores.
In treatments commonly referred to as "acidizing", an aqueous acid solution is pumped into the formation to increase the size of existing pores and to etch new flow channels therein. In treatments known as "fracturing", a fluid is forced into the formation under a pressure and at a rate such that one or more fractures in the formation are produced. An acid solution can be introduced into the fractures to etch flow channels and enlarge existing pore spaces in the faces thereof, and fluids carrying sand, walnut hulls and/or other small particles can be introduced into the fractures to keep the fractures open.
Special chemicals are typically admixed with acidizing, fracturing and other treatment fluids to increase the effectiveness thereof. For example, various surface active agents and mutual solvents are often admixed with treatment fluids to enhance the wetting ability of the fluids, to lower the interfacial tension between the fluids and oil and/or to lower the surface tension of the fluids. The treatment fluids are often used in the form of emulsions or micellar solutions to impart properties to the fluids that they would not otherwise have. The type of special chemicals and treatment system employed for a particular application depends on well characteristics and conditions, economics and the result desired.
In many instances, the ability of a treatment fluid to penetrate into the formation is limited due to the naturally low permeability of the formation rock or due to formation damage resulting from fines migration and/or partial plugging with organic and inorganic substances such as paraffin and asphaltene, drilling mud and thick emulsion sludges formed of water from the treatment fluid and oil. In other instances, natural circumstances such as the existence of an undesirable water zone above or below the formation being treated prevents the use of a pressure sufficient to force the treatment fluid deep into the formation or to initiate a fracture Unfortunately, the special chemicals and treatment systems currently available do not always effectively overcome these problems.
By the present invention, improved well treatment compositions and a method of treating a subterranean formation with the same are provided. The inventive compositions and method are particularly effective for use in naturally tight or damaged formations and in applications where the amount of pressure normally required to force the treatment fluid deep into the formation or to initiate a fracture cannot be employed.